public class BinaryTree {

    static class TreeNode {
        public char val;
        public TreeNode left;//左孩子的引用
        public TreeNode right;//右孩子的引用

        public TreeNode(char val) {
            this.val = val;
        }
    }


    /**
     * 创建一棵二叉树 返回这棵树的根节点
     *
     * @return
     */
    public TreeNode createTree() {
        TreeNode A=new TreeNode('A');
        TreeNode B=new TreeNode('B');
        TreeNode C=new TreeNode('C');
        TreeNode D=new TreeNode('D');
        TreeNode E=new TreeNode('E');
        TreeNode F=new TreeNode('F');
        TreeNode G=new TreeNode('G');
        TreeNode H=new TreeNode('H');
        A.left=B;
        A.right=C;
        B.left=D;
        B.right=E;
        C.left=F;
        C.right=G;
        E.right=H;
        return A;

    }

    // 前序遍历
    public void preOrder(TreeNode root) {
        if(root==null){
            return;
        }
        System.out.print(root.val+" ");
        preOrder(root.left);
        preOrder(root.right);
    }

    // 中序遍历
    void inOrder(TreeNode root) {
        if(root==null){
            return;
        }
        inOrder(root.left);
        System.out.print(root.val+" ");

        inOrder(root.right);

    }

    // 后序遍历
    void postOrder(TreeNode root) {
        if(root==null){
            return;
        }
        postOrder(root.left);
        postOrder(root.right);
        System.out.print(root.val+" ");
    }

    public static int nodeSize;

   /* *
     * 获取树中节点的个数：遍历思路
     */
    void size(TreeNode root) {
    }

/*    *
     * 获取节点的个数：子问题的思路
     *
     * @param root
     * @return*/

  /*  int size2(TreeNode root) {
    }*/



     //获取叶子节点的个数：遍历思路

    public static int leafSize = 0;

    void getLeafNodeCount1(TreeNode root) {
        if(root==null){
            return;
        }
        if(root.left==null&&root.right==null){
            leafSize++;
        }
        getLeafNodeCount1(root.left);
        getLeafNodeCount1(root.right);
    }


   //  获取叶子节点的个数：子问题

    int getLeafNodeCount2(TreeNode root) {
        if(root==null){
            return 0;
        }
        if(root.left==null&&root.right==null){
            return 1;
        }
      return  getLeafNodeCount2(root.left)+ getLeafNodeCount2(root.right);

    }

 //获取第K层节点的个数

    int getKLevelNodeCount(TreeNode root, int k) {
        if(root==null){
            return 0;
        }
        if(k==1){
            return 1;
        }
        return getKLevelNodeCount(root.left,k-1)+getKLevelNodeCount(root.right,k-1);
    }
     /*获取二叉树的高度
     时间复杂度：O(N)*/

    int getHeight(TreeNode root) {
        if(root==null){
            return 0;
        }
        int leftHeight=getHeight(root.left);
        int rightHeight=getHeight(root.right);
     //  return Math.max(leftHeight,rightHeight)+1;
        return (leftHeight>rightHeight? leftHeight:rightHeight)+1;
       
    }


    // 检测值为value的元素是否存在
    TreeNode find(TreeNode root, char val) {
        if(root==null){
            return null;
        }
        if(root.val==val){
            return root;
        }
        TreeNode findLeft=find(root.left,val);
        if(findLeft!=null){
            return findLeft;
        }
        TreeNode findRight=find(root.right,val);
        return findRight;
    }


}